The present invention relates to a device for decoding video data and audio data and its method, and specifically relates to special reproduction techniques for video data.
A technique for encoding video signals and audio signals for television using an encoding technique such as an MPEG (moving picture experts group) or the like, and transmitting or recording/reproducing them, will be generalized.
The above MPEG is constructed so that decoding and displaying timings of a video signal and an audio signal are synchronized using time stamps added to them bit streams, in a decoder at a receiving side or a reproducing side. And if video is frozen in the decoder, audio is muted because the timings cannot be synchronized using the time stamps.
An application which outputs audio even if video is frozen is desired. However, it causes a problem that if audio is outputted in the state where video is frozen, it takes a time to synchronize video and audio when the freeze is next released.
Considering the above point, the present invention aims to output audio even if video is frozen in an MPEG decoder or the like. Furthermore, the present invention aims to output a motion picture by returning immediately after a release from freeze. Moreover, the present invention aims to synchronize video with audio immediately after a release from freeze.
To solve above problem, in an information signal decoding method of the present invention, plural areas to store decoded motion picture data are prepared. Freeze and continuous output of the motion picture data are performed using one of said plural areas. Intraframe predicted pictures and forward predicted pictures in a data stream of motion pictures to be inputted in said freeze are decoded using the other areas. A data stream of audio is decoded while keeping a synchronous relationship with motion pictures.
Furthermore, in the information signal decoding method according to the present invention, in said decoding using the other areas, channel switching is prepared by decoding the data stream of motion pictures of a channel different from the frozen motion picture, and either of the frozen motion picture or the motion picture of the different channel is selected to selectively switch a channel.
An information signal decoding device according to the present invention provides a first decoding means for decoding a data stream of motion pictures, a second decoding means for decoding a data stream of audio, a motion picture data storing means having plural areas to store the decoded motion picture data, and a control means for synchronizing the decoding of motion picture data and the decoding of audio data. In this device, freeze and continuous output of motion picture data are performed using one of said plural areas, and intraframe predicted pictures and forward predicted pictures in a data stream of motion pictures to be inputted in a freeze are decoded using the other areas. A data stream of audio is decoded while keeping a synchronous relationship with said motion pictures.
The information signal decoding device according to the present invention further comprises a switching means for switching said plural areas for output, and a selecting means for selecting an area to be switched by the above switching means, to selectively switch a channel.
Moreover, in the information signal decoding method according to the present invention, at the time of write-in or readout in one of said plural areas, intraframe predicted pictures and forward predicted pictures in a data stream of motion pictures are decoded using the other areas, and the decoded motion picture data is outputted to said single area as a reduced picture.
An information signal decoding device according to the present invention comprises a decoding means for decoding a data stream of motion pictures, a motion picture data storing means having plural areas to store decoded motion picture data, and a picture reducing means for generating reduced picture data from the decoded motion picture data. In this device, at the time of write-in or readout in one of said plural areas, intraframe predicted pictures and forward predicted pictures in a data stream of motion pictures are decoded using the other areas, and the decoded motion picture is outputted to said single area as a reduced picture.
According to the present invention, freeze and continuous output of motion picture data are performed using one of plural areas in a motion picture storing means, and intraframe predicted pictures and forward predicted pictures in a data stream of motion pictures to be inputted in a freeze are decoded using the other areas. Besides, a data stream of audio is decoded while keeping a synchronous relationship with motion pictures.
Furthermore, according to the present invention, at the time of write-in or readout in one of said plural areas, intraframe predicted pictures and forward predicted pictures in a data stream of motion pictures are decoded using the other areas, and the decoded motion picture data is outputted to said single area as a reduced picture.
Moreover, according to the present invention, the function of special effects such as strobe reproduction, channel scanning, etc., can be realized.